In many piston powered units, such as compressors and internal combustion engines, full floating piston or wrist pins are used to operatively connect connecting rods with pistons for operating in an associated cylinder. Such pins advantageously provide two stages or levels of pin freedom for reducing pin and bearing friction and wear. When properly installed in a piston and rod assembly, these pins possess the capability of turning in the pin bearing, or bores, of laterally spaced bosses of the piston and also relative to the pin bearing or bushing at the small end of the connecting rod through which the pin extends.
Axial thrust loads applied to wrist pins, such as from the sideways movement of the connecting rod during piston stroking in the associated cylinder, may cause the wrist pin to slide axially in the pin bores. If the pin is displaced to a point at which one end of the pin physically contacts and rubs against the cylinder wall, the cylinder and the piston are subject to damage often necessitating labor intensive and expensive repair.
To prevent such occurrences, wire end locks or snap rings are operatively mounted in the bores of the pin bosses at outboard of the ends of the pin to trap the pin in a substantially centered position. With the pin so held within confines of the pin boss bores and away from the cylinder walls, pin damage to the cylinder and piston is obviated. An example of such pin retention is found in Auto Service and Repair, M. W. Stockel et al., The Goodheart-Willcox Co., Inc., Page 280, C 1978.
In addition to wire end locks, a wide variety of other retainers have been used for similar purposes. For example, retainer clips such as shown in U.S. Pat. No. 5,367,945, issued Nov. 29, 1994 to Halka, et al., and split and two piece bearings, such as shown in U.S. Pat. No. 1,491,151, issued Apr. 22, 1924 to L. J. McKone, are used to secure wrist pins in operative position.
While these pin retention structures and methods may be satisfactory for some installations, they require special bearing structures or separate retention components which add to the cost burden of piston and connecting rod assemblies and are subject to failure, misassembly, and shortened service life, particularly, since they generally operate in a harsh environment such as in internal combustion engines.